U.S. patent application number 14/111646 was filed with the patent office on 2014-05-01 for additive composition for caustic removable hot melt adhesives and formulations containing the same.
This patent application is currently assigned to Cray Valley USA, LLC. The applicant listed for this patent is William R. Dougherty, Nestor P. Hansen. Invention is credited to William R. Dougherty, Nestor P. Hansen.
Application Number | 20140120280 14/111646 |
Document ID | / |
Family ID | 45976542 |
Filed Date | 2014-05-01 |
United States Patent
Application |
20140120280 |
Kind Code |
A1 |
Dougherty; William R. ; et
al. |
May 1, 2014 |
ADDITIVE COMPOSITION FOR CAUSTIC REMOVABLE HOT MELT ADHESIVES AND
FORMULATIONS CONTAINING THE SAME
Abstract
An additive composition for imparting caustic removability to a
hot melt adhesive includes an ester functionalized polymer having a
polymeric backbone and, pendent thereon, one or more dicarboxylic
acid moieties in at least partial ester form. The polymeric
backbone has a weight average molecular weight less than 50,000.
The ester functionalized polymer may be, for example, an at least
partial ester of a maleated hydrocarbon. The additive may further
include a low molecular weight .alpha.,.beta. ethylenically
unsaturated anhydride-containing or acid-containing polymer. A
caustic removable hot melt adhesive composition comprises a hot
melt adhesive additive and a conventional hot melt adhesive resin.
A caustic removable adhesive label comprises a substrate and a
caustic removable hot melt adhesive composition which includes an
additive composition. The caustic removable hot melt adhesives can
be used on labels for articles, such as glass bottles.
Inventors: |
Dougherty; William R.;
(Lancaster, PA) ; Hansen; Nestor P.; (Coatesville,
PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Dougherty; William R.
Hansen; Nestor P. |
Lancaster
Coatesville |
PA
PA |
US
US |
|
|
Assignee: |
Cray Valley USA, LLC
Exton
PA
|
Family ID: |
45976542 |
Appl. No.: |
14/111646 |
Filed: |
April 11, 2012 |
PCT Filed: |
April 11, 2012 |
PCT NO: |
PCT/US12/33026 |
371 Date: |
January 14, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61475756 |
Apr 15, 2011 |
|
|
|
Current U.S.
Class: |
428/34.7 ;
428/349; 428/35.7; 428/35.9; 524/112; 524/315 |
Current CPC
Class: |
Y10T 428/1321 20150115;
Y10T 428/1359 20150115; C08F 8/14 20130101; C08G 2170/20 20130101;
C08F 8/14 20130101; C09J 11/08 20130101; C08L 91/00 20130101; C08F
222/06 20130101; Y10T 428/1352 20150115; C08K 5/11 20130101; C09J
153/02 20130101; C08F 240/00 20130101; C08F 212/08 20130101; C08F
222/08 20130101; C08F 289/00 20130101; C08F 8/46 20130101; C08K
5/1539 20130101; Y10T 428/2826 20150115; C08F 8/14 20130101; C08L
35/06 20130101; C08F 212/08 20130101; Y02P 20/582 20151101; G09F
3/10 20130101; C08F 8/14 20130101; C08F 8/14 20130101; C08F 212/08
20130101; C09J 11/06 20130101 |
Class at
Publication: |
428/34.7 ;
524/315; 524/112; 428/349; 428/35.7; 428/35.9 |
International
Class: |
C09J 11/08 20060101
C09J011/08; G09F 3/10 20060101 G09F003/10; C09J 7/02 20060101
C09J007/02; C08K 5/11 20060101 C08K005/11; C08K 5/1539 20060101
C08K005/1539 |
Claims
1. An additive composition for imparting caustic removability to a
hot melt adhesive, said additive composition comprising: an ester
functionalized polymer comprising a polymeric backbone and, pendent
thereon, one or more dicarboxylic acid moieties in at least partial
ester form; and an at least partial ester of a low molecular weight
.alpha.,.beta. ethylenically unsaturated anhydride-containing or
acid-containing polymer selected from the group consisting of a
partial ester of a low molecular weight maleic anhydride
homopolymer, a partial ester of a low molecular weight maleic
anhydride olefin copolymer, and partial ester of a low molecular
weight maleic anhydride vinyl aromatic copolymer.
2. The additive composition of claim 1, wherein a portion of the
polymeric backbone is aliphatic.
3. The additive composition of claim 1, wherein the polymeric
backbone has a weight average molecular weight less than
50,000.
4. The additive composition of claim 1, wherein the polymeric
backbone is a homopolymer of a C3 to C16 monomer or a copolymer of
two or more C3 to C16 monomers.
5. The additive composition of claim 1, wherein the one or more
dicarboxylic acid moieties is an at least partial ester of a
dicarboxylic acid moiety derived from a functionalizing agent
selected from the group consisting of maleic acid, maleic
anhydride, fumaric acid, itaconic acid, tetrahydrophthalic acid,
and tetrahydrophthalic anhydride.
6. The additive composition of claim 1, wherein the ester
functionalized polymer is an at least partial ester of a maleic
anhydride grafted butadiene polymer or an at least partial ester of
a maleic anhydride grafted C5 hydrocarbon polymer.
7. The additive composition of claim 1, wherein the ester
functionalized polymer is an at least partial ester of a maleic
anhydride grafted hydrocarbon polymer containing a structure
according to Formula I: ##STR00004## wherein R is a maleic
anhydride or a dicarboxylic acid moiety, the dicarboylic acid
moiety having a structure according to Formula II: ##STR00005##
wherein R.sup.1 and R.sup.2 can be the same or different and are
selected from H and any residue of an aromatic, aliphatic, linear,
or branched C1-C12 monoalcohol, provided that at least a portion of
the acid groups in the polymer are in ester form.
8. The additive composition of claim 1, wherein the at least
partial ester of a low molecular weight .alpha.,.beta.
ethylenically unsaturated anhydride-containing or acid-containing
polymer is a partial ester of a low molecular weight maleic
anhydride vinyl aromatic copolymer.
9. The additive composition of claim 1, wherein the at least
partial ester of a low molecular weight .alpha.,.beta.
ethylenically unsaturated anhydride-containing or acid-containing
polymer is a partial ester of a low molecular weight styrene-maleic
anhydride (SMA) copolymer.
10. The additive composition of claim 9, wherein the low molecular
weight styrene-maleic anhydride (SMA) copolymer has a structure
according to Formula III: ##STR00006## in which R is a residue of
at least one monoalcohol selected from C1 to C12 monoalcohols, and
their mixtures; n ranges from 7 to 72; and x, y, and z are such
that a molar ratio of (x:(y+z)) is in the range from 1:1 to 3:1,
and (z/(y+z)) ranges from 0.5 to 1.0.
11. The additive composition of claim 10, wherein the low molecular
weight SMA ester has a ratio of styrene(S) : maleic anhydride(MA)
of about 1:1 to about 3:1.
12. The additive composition of claim 10, wherein the low molecular
weight SMA ester has a ratio of styrene(S) : maleic anhydride(MA)
of about 1.4:1 to about 1.6:1.
13. The additive composition of claim 8, wherein the ester
functionalized polymer is an at least partial ester of a maleic
anhydride grafted hydrocarbon polymer and the at least partial
ester of a low molecular weight maleic anhydride vinyl aromatic
copolymer is a partial ester of a low molecular weight
styrene-maleic anhydride (SMA).
14. A caustic removable hot melt adhesive composition comprising: a
hot melt adhesive additive comprising the additive composition of
claim 1; and an adhesive resin selected from the group consisting
of styrene-isoprene block copolymers, polyacrylate resins, poly
ethylene vinyl acetate (EVA) resins, polystyrene butadiene resins,
random styrene butadiene (SBR) copolymers, styrene-butadiene block
copolymers, styrene-isoprene-butadiene-styrene block copolymers,
styrene-ethylene-propylene-styrene block copolymers,
styrene-ethylene-butylene block copolymers, amorphous poly-.alpha.
olefin (APAO) resins, and mixtures thereof.
15. A caustic removable adhesive label comprising: a substrate, and
a caustic removable hot melt adhesive composition comprising a hot
melt adhesive additive comprising the additive composition of claim
1; and an adhesive resin selected from the group consisting of
styrene-isoprene block copolymers, hydrocarbon tackifying resins,
polyacrylate resins, poly ethylene vinyl acetate (EVA) resins,
polystyrene butadiene resins, random styrenebutadiene (SBR)
copolymers, styrene-butadiene block copolymers,
styrene-ethylene-butylene block copolymers, amorphous poly-.alpha.
olefin (APAO) resins, and mixtures thereof.
16. (canceled)
17. The caustic removable adhesive label of claim 15, wherein the
adhesive additive is soluble in a caustic solution having a pH
greater than 8.
18. An article having a caustic removable adhesive label, wherein
the article comprises a container, and a caustic removable adhesive
label according to claim 15.
19. The article of claim 18, wherein the container is made from a
material from the group consisting of glass, metal, and
plastic.
20. The additive composition of claim 1, wherein the one or more
dicarboxylic acid moieties are 50 to 100% esterified.
21. The additive composition of claim 1, wherein the one or more
dicarboxylic acid moieties contain one or two ester groups having a
structure --C(.dbd.O)OR wherein R is a C1 to C6 alkyl group.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a U.S. National Phase Application of PCT
International Application PCT/US2012/033026 which claims the
benefit of U.S. Provisional Application No. 61/475,756, filed Apr.
15, 2011, the contents of which are incorporated herein in their
entireties for all purposes.
FIELD OF INVENTION
[0002] This invention relates to hot melt adhesive formulations
which have properties enabling caustic removability. More
particularly, the invention relates to an adhesive additive
composition for imparting caustic removability to a hot melt
adhesive. Additionally, this invention relates to the hot melt
adhesive composition including the additive composition, to the
adhesive labels which employ the hot melt adhesive composition, and
to the articles upon which the adhesive label is adhered with the
adhesive composition of the invention.
BACKGROUND OF THE INVENTION
[0003] Hot melt adhesives typically exist as entirely solid
materials which do not contain or require any solvents. They are
solid materials at ambient room temperature but can be converted to
a flowable liquid or fluid state by the application of heat, in
which state they may be applied to a substrate. On cooling, the
adhesive regains its solid form and gains its cohesive strength. In
this regard, hot melt adhesives differ from other types of
adhesives, such as water-based adhesives, which achieve the solid
state by evaporation, removal of solvents, polymerization, or other
means.
[0004] These adhesives are particularly useful in the manufacture
of a variety of industrial or consumer goods where bonding of
various substrates is necessary. An advantage of hot melt adhesives
is the absence of a liquid carrier, as would be the case for
water-based or solvent-based adhesives, which requires a drying
step during application of the adhesive. Suitable hot melt
adhesives possess the appropriate bond strength to adhere the
substrates involved, and also demonstrate adequate flexibility, no
staining or bleedthrough of the substrate, suitable viscosity and
open time to function on a variety of substrates, acceptable
stability under storage conditions, and acceptable thermal
stability under normal application temperature.
[0005] Hot melt adhesives may be formulated to be relatively hard
and free of tack or, in contrast, to be pressure sensitive, i.e.,
relatively soft and tacky at room temperature. Hot melt adhesives
are increasingly utilized for affixing labels to various
substrates, such as to glass or plastic bottles. Pressure sensitive
hot melt adhesives for labeling are usually categorized as either
removable or permanent. Permanent adhesives are formulated to cause
the label to tear upon removal from the substrate. On the contrary,
removable adhesives must allow the label to be removed from the
substrate with a clean release, i.e., leaving no residue and
without the tear of the label stock which occurs in a permanent
adhesive application.
[0006] Solid hot melt adhesives for permanent adhesives have been
widely used for many years. However, a hot melt adhesive, and more
particularly a hot melt pressure sensitive adhesive, that gives
good removability has not been available. Current removable
adhesives are supplied for label stock from acrylic latices and
solvented solution adhesives. Both of these materials have high
molecular weight polymers that reduce flow on a surface to prevent
build up of adhesion. In contrast, hot melt adhesives, in
particular hot melt pressure sensitive adhesives, are based on
materials having lower molecular weight polymers and high amounts
of very low molecular weight components that make reduced flow or
wetting on a surface very difficult.
[0007] Many different polymers have been used in hot melt adhesives
employed in the construction of industrial or consumer goods.
Typical hot melt adhesives have employed polymers which have
included tri-block copolymers such as styrene-isoprene-styrene
(SIS); styrene-butadiene-styrene (SBS);
styrene-isoprene-butadiene-styrene (SIBS);
styrene-ethylene-propylene-styrene (SEPS);
styrene-ethylene-butylene-styrene (SEBS); ethylene-vinyl acetate
(EVA) copolymers; and/or amorphous poly-alpha-olefin (APAO).
Although these polymers, when properly blended, provide adhesion to
most substrates, they are not suitable for certain particular uses.
One shortcoming of the prior hot melt adhesives concerns their
removability, which is an important feature for purposes of
recycling the substrate.
[0008] To improve removability of the hot melt adhesive, the prior
art has aimed to increase the water-solubility or
water-dispersibility characteristics of the adhesive. For example,
one known water sensitive hot melt adhesive composition which may
be utilized in the manufacturing of disposable goods, especially
disposable nonwoven articles, combines high dry bond strength with
increased water solubility, thereby permitting the component
elements of the disposable article to be recycled or otherwise
disposed of in an environmentally friendly manner (i.e., degraded).
Other known adhesives relate to a water-soluble or
water-dispersible hot melt composition based on graft copolymers.
These water-removable hot melt adhesives are used for labelling
returnable bottles at high speeds, wherein the labels can be
removed by brief soaking in hot water. However, these water-soluble
compositions are not favorably employed to adhere labels to glass
bottles, where water-resistant characteristics are desired as much
as the clean removability of pressure sensitive labels.
[0009] Conventional styrene-isoprene-styrene (SIS) block
copolymer/hydrocarbon (HC) tackifier-based hot melt adhesives have
been used to adhere labels to glass bottles for decades. One of the
beneficial properties of these types of adhesives for this
application is that they can withstand a 7-day water immersion
test. Accordingly, these types of adhesives are known for their
favorable water-resistant characteristics. However, this presents a
difficult challenge when the labels and adhesives need to be
removed in a glass bottle recycling process. Hot caustic baths are
successfully used to remove many water-based label adhesives.
However, the hot melt adhesives are very resistant to caustic.
SUMMARY OF THE INVENTION
[0010] A new additive has now been developed which imparts caustic
removability to conventional hot melt adhesives without
significantly sacrificing adhesive performance. For example,
particular additives of the present invention impart caustic
removability to styrene-isoprene-styrene (SIS) block
copolymer/hydrocarbon (HC) tackifier-based hot melt adhesives. An
adhesive containing the additive may be formulated to achieve
similar water resistance and adhesive strength properties as when
the additive is not present, while enabling the complete
removability of the labels in caustic baths for recycling purposes.
The adhesive containing the additive may be applied to a substrate,
such as paper for an adhesive label, for adhesion to an article
such as a glass bottle or container. The presence of such an
additive in a hot melt adhesive composition improves the caustic
removability of the adhesive while maintaining the viscoelastic
performance characteristics and adhesive properties of the hot melt
adhesive composition.
[0011] The present invention relates to an adhesive additive
composition for imparting caustic removability to a hot melt
adhesive. Additionally, this invention relates to a hot melt
adhesive composition, particularly a hot melt pressure sensitive
adhesive composition, which includes the adhesive additive
composition. The present invention also relates to a hot melt
adhesive label, which includes the hot melt adhesive composition
and the adhesive additive composition, that is removable by a
caustic solution. Furthermore, the invention relates to an article
upon which the adhesive label is adhered with use of the adhesive
composition of the invention.
[0012] According to a first embodiment, the present invention
relates to an additive composition for imparting caustic
removability to a hot melt adhesive. The additive composition
comprises an ester functionalized polymer comprising a polymeric
backbone and, pendent thereon, one or more dicarboxylic acid
moieties in at least partial ester form. The terms "polymer" and
"resin" are to be interpreted in the present invention as having
the same meaning, namely a naturally occurring or synthetic
compound consisting of large molecules made up of a linked series
of repeated monomers obtained by, for example, a polymerization
process. In at least one embodiment of the present invention, the
polymeric backbone is aliphatic. In other embodiments, the
polymeric backbone may contain aliphatic as well as aromatic
repeating units. The polymeric backbone has a low molecular weight.
As used herein, the term "low molecular weight" means an average
molecular weight less than about 50,000. In some embodiments of the
present invention, the ester functionalized polymer is an at least
partial ester of a maleic anhydride grafted hydrocarbon polymer.
The term "graft copolymer" is meant to mean a polymer in which the
main backbone chain has attached to it at various points side
chains containing different atoms or groups from those in the main
chain. The main chain may be a copolymer or may be derived from a
single monomer.
[0013] In at least one particular embodiment, the additive
composition further comprises a low molecular weight 0,13
ethylenically unsaturated anhydride-containing or acid-containing
polymer selected from the group consisting of low molecular weight
maleic anhydride homo-polymers and at least partial esters thereof,
low molecular weight maleic anhydride olefin copolymers and at
least partial esters thereof, and low molecular weight maleic
anhydride vinyl aromatic copolymers and at least partial esters
thereof, and combinations and mixtures thereof. In some embodiments
of the present invention, the additive composition includes a low
molecular weight maleic anhydride vinyl aromatic copolymer or an at
least partial ester thereof, such as a low molecular weight
styrene-maleic anhydride (SMA) or an at least partial ester
thereof.
[0014] In a preferred example of this embodiment, the additive
composition comprises a combination of polymers. Exemplary
compositions of the present invention include, for example, an
ester functionalized polymer comprising a polymeric backbone and,
pendent thereon, one or more dicarboxylic acid moieties in at least
partial ester form; and a low molecular weight maleic anhydride
vinyl aromatic copolymer or an at least partial ester thereof. For
example, in at least one embodiment of the present invention, the
additive may include (i) an at least partial ester of a maleic
anhydride grafted hydrocarbon polymer and (ii) a low molecular
weight styrene-maleic anhydride (SMA) or an at least partial ester
thereof.
[0015] The additive compositions of the present invention impart
caustic removal properties to a conventional hot melt adhesive
formulation. Adhesives formulated with such additives can be used
in hot melt adhesive labels, particularly in hot melt pressure
sensitive labels for recyclable glass articles, such as bottles.
The labels can be removed with caustic, such as in a hot caustic
bath, when the objects are recycled. Without being held to the
theory, it is believed that the acid and/or anhydride groups of the
additive components impart caustic solubility to the otherwise
insoluble hot melt adhesive components. The dicarboxylic acids, in
at least partial ester form, of the ester functionalized polymer
component are believed to contribute to the desirable properties of
the additive and the resulting adhesive formulation. For example,
the additive imparts caustic solubility to the hot melt adhesive
composition comprising a block copolymer, such as a
styrene-isoprene-styrene (SIS) block copolymer; a tackifying resin,
such as a hydrocarbon resin; and a process oil, such as mineral
oil. The desired adhesive properties of the hot melt adhesive are
retained even though the caustic removability property has been
imparted by the addition of the additive.
[0016] In another embodiment, the present invention is a caustic
removable hot melt adhesive composition, more particularly a hot
melt pressure sensitive adhesive composition, which includes a hot
melt adhesive additive. The hot melt adhesive composition is
caustic removable and includes a hot melt adhesive additive which
comprises an ester functionalized polymer comprising a polymeric
backbone and, pendent thereon, one or more dicarboxylic acid
moieties in at least partial ester form; and an adhesive resin
selected from the group consisting of styrene-isoprene block
copolymers, polyacrylate resins, poly ethylene vinyl acetate (EVA)
resins, polystyrene butadiene resins, random styrenebutadiene (SBR)
copolymers, styrene-butadiene block copolymers,
styrene-ethylene-butylene-styrene (SEBS) block copolymers,
amorphous poly-.alpha. olefin (APAO) resins, and mixtures thereof.
In at least one particular embodiment, the additive composition
further comprises a low molecular weight .alpha.,.beta.
ethylenically unsaturated anhydride-containing or acid-containing
polymer selected from the group consisting of low molecular weight
maleic anhydride homo-polymers and at least partial esters thereof,
a low molecular weight maleic anhydride olefin copolymers and at
least partial esters thereof, and low molecular weight maleic
anhydride vinyl aromatic copolymers and at least partial esters
thereof, and combinations and mixtures thereof. In a preferred
example of this embodiment, the additive composition comprises an
ester functionalized polymer comprising a polymeric backbone and,
pendent thereon, one or more dicarboxylic acid moieties in at least
partial ester form; and a low molecular weight maleic anhydride
vinyl aromatic copolymer or an at least partial ester thereof. For
example, in at least one embodiment of the present invention, the
additive may include (i) an at least partial ester of a maleic
anhydride grafted hydrocarbon polymer and (ii) a low molecular
weight styrene-maleic anhydride (SMA) copolymer or an at least
partial ester thereof. The present invention has a particular
usefulness for labels on products which are to be recycled.
[0017] In yet another embodiment, the present invention is a
caustic removable adhesive label comprising a substrate and a
caustic removable hot melt adhesive composition comprising a hot
melt adhesive additive. The hot melt adhesive additive comprises an
ester functionalized polymer comprising a polymeric backbone and,
pendent thereon, one or more dicarboxylic acid moieties in at least
partial ester form; and an adhesive resin selected from the group
consisting of styrene-isoprene block copolymers (such as
styrene-isoprene-styrene (SIS) block copolymers), hydrocarbon
tackifying resins, polyacrylate resins, poly ethylene vinyl acetate
(EVA) resins, polystyrene butadiene resins, random styrenebutadiene
(SBR) copolymers, styrene-butadiene block copolymers (such as a
styrene-butadiene-styrene (SBS) block copolymer),
styrene-ethylene-butylene block copolymers (such as a
styrene-ethylene-butylene-styrene (SEBS) block copolymer),
amorphous poly-.alpha. olefin (APAO) resins, and mixtures thereof.
The adhesive composition is applied to the substrate for adhesion
to an article. The label of the present invention may be a label
which, after application of the caustic removable hot melt adhesive
composition, may be adhered to an article such as a glass bottle.
In at least one embodiment, the caustic removable adhesive label
contains a hot melt adhesive composition including an additive
composition, in which the additive composition comprises a
combination of polymers. Exemplary two-part additive compositions
of the present invention include, for example, an ester
functionalized polymer comprising a polymeric backbone and, pendent
thereon, one or more dicarboxylic acid moieties in at least partial
ester form; and a low molecular weight maleic anhydride vinyl
aromatic copolymer or an at least partial ester thereof. For
example, in at least one embodiment of the present invention, the
additive may include (i) an at least partial ester of a maleic
anhydride grafted hydrocarbon polymer and (ii) a low molecular
weight styrene-maleic anhydride (SMA) or an at least partial ester
thereof. The adhesive additive may be soluble at room temperature
in a caustic (basic) solution having a pH greater than 8.
[0018] In another embodiment, the present invention is an article
having a caustic removable adhesive label. Particularly, the
article is a container and a caustic removable adhesive label is
adhered thereto. The label comprises a substrate, such as paper,
and a caustic removable hot melt adhesive composition having an
additive which comprises an ester functionalized polymer comprising
a polymeric backbone, pendent thereon, one or more dicarboxylic
acid moieties in at least partial ester form. The additive may be
soluble in a caustic solution having a pH greater than 8. The
container may be made of any suitable material including, for
example, glass, metal (e.g., stainless steel), or plastic (e.g., a
polyolefin such as high density polyethylene). The label adheres to
the article with good adhesion properties, and the article and
label are water resistant. The label becomes removable from the
article upon being submerged in, or otherwise treated with, a
caustic bath having a pH greater than 8.
DETAILED DESCRIPTION OF THE INVENTION
[0019] The additive composition of the present invention, which
imparts the caustic removability property to a conventional hot
melt adhesive formulation, comprises an ester functionalized
polymer comprising a polymeric backbone and, pendent thereon, one
or more dicarboxylic acid moieties in at least partial ester form.
More particularly, the ester functionalized polymer includes a
polymeric backbone that may be aliphatic. The polymeric backbone
has a low molecular weight defined as a weight average molecular
weight less than about 50,000. The polymeric backbone may be, for
example, a homopolymer of a C3 to C16 monomer or a copolymer of two
or more C3 to C16 monomers. The one or more dicarboxylic acid
moieties may be, for example, an at least partial ester of a
dicarboxylic acid moiety. Such dicarboxylic acid moieties may be
derived from, for example, a functionalizing agent selected from
the group consisting of maleic acid, maleic anhydride, fumaric
acid, itaconic acid, tetrahydrophthalic acid, and
tetrahydrophthalic anhydride.
[0020] In some embodiments of the present invention, the ester
functionalized polymer is an at least partial ester of a maleic
anhydride grafted hydrocarbon polymer. The term "hydrocarbon
polymer," as used herein, is meant to define a class which includes
those hydrocarbons copolymerized with styrenically
aromatic-containing hydrocarbon monomers, up to and including C10
hydrocarbons. For example hydrocarbon polymers may contain alpha
methyl styrene, indene, or other C4-C10 hydrocarbons. In such
embodiments, the pendent dicarboxylic acid ester functional groups
may be directly introduced onto the polymer backbone by a grafting
reaction using, for example, an ester of maleic acid.
Alternatively, a diacid or anhydride functionalizing agent, such as
maleic anhydride, may be grafted onto the polymeric backbone and
then reacted, for example, with an alcohol to form the ester,
reacting 25 to 100% of the available anhydride functionality. The
maleic anhydride grafted polymer may also be hydrogenated to remove
unsaturation before being esterified. As used herein, the term
"maleic anhydride grafted polymer" is equivalent to a "maleated
polymer" or a "maleinized polymer," such that a maleic anhydride
functionalizing agent is grafted or otherwise affixed to the
polymeric backbone to form a maleated or maleinized polymer.
[0021] In at least one embodiment of the present invention, the
ester functionalized polymer is an at least partial ester of a
maleic anhydride grafted hydrocarbon polymer containing a structure
according to Formula I:
##STR00001##
wherein R is maleic anhydride or a dicarboxylic acid moiety, the
dicarboylic acid moiety having a structure according to Formula
II:
##STR00002##
wherein R.sup.1 and R.sup.2 can be the same or different and are
selected from H and any residue of an aromatic, aliphatic, linear,
or branched C1-C12 monoalcohol, preferably a C2-C8 monoalcohol,
provided that at least a portion of the acid groups in the polymer
are in ester form, approximately 25 to 100% esterification. A
person with ordinary skill in the art would appreciate that Formula
I is a representation of some of the possible structures and
configurations of a polymeric hydrocarbon. The maleic anhydride
grafted polymer may also be hydrogenated to remove unsaturation
before being esterified. The monoalcohol may be alkoxylated, such
as with up to 16 alkoxy units from an ethoxy group and/or a propoxy
group. The resin of Formula I can be any partially maleated
hydrocarbon resin that is soluble to any degree in basic pH
solutions. These maleated polymeric hydrocarbon resins have
anhydride functionality. The degree of maleinization (or maleation)
of the polymeric hydrocarbon can range from the least amount needed
to render a given hydrocarbon partially soluble in a basic pH
solution having a pH greater than 8, to as high a level of
maleinization as is achievable, while retaining compatibility with
the hot melt adhesive formulation components. The maleated
polymeric hydrocarbon copolymer may have, for example, a maleic
anhydride content (i.e., is maleated or maleinized) from 1% to 50%
wt/wt, more preferably 5% to 30% wt/wt. In a preferred embodiment
of the present invention, the additive composition includes a 9%
maleated derivative of a polymeric hydrocarbon which has been at
least partially esterified with an alcohol.
[0022] In at least one particular embodiment, the additive
composition further comprises a low molecular weight .alpha.,.beta.
ethylenically unsaturated anhydride-containing or acid-containing
polymer selected from the group consisting of low molecular weight
maleic anhydride homo-polymers and at least partial esters thereof,
low molecular weight maleic anhydride olefin copolymers and at
least partial esters thereof, and low molecular weight maleic
anhydride vinyl aromatic copolymers and at least partial esters
thereof, and combinations and mixtures thereof. In some embodiments
of the present invention, the additive composition includes a low
molecular weight maleic anhydride vinyl aromatic copolymer or an at
least partial ester thereof, such as a low molecular weight
styrene-maleic anhydride (SMA) or an at least partial ester
thereof.
[0023] In a particular embodiment of the present invention, the low
molecular weight .alpha.,.beta. ethylenically unsaturated
anhydride-containing or acid-containing polymer which may be
copolymers of the anhydride or acid with a co-monomer selected from
vinyl aromatic monomers such as, for example, vinyl toluenes and
styrene, or from ethylene and/or propylene. Preferably, the molar
ratio of the co-monomer to the anhydride or acid ranges from about
1:1 to 3:1. The carboxylic anhydride vinyl aromatic copolymer is
partially esterified by an alcohol, more particularly by a
monoalcohol. For example, the carboxylic anhydride vinyl aromatic
monomer copolymer may be at least partially esterified by an
aromatic, aliphatic, linear, or branched C1-C12 monoalcohol,
preferably a C2-C8 monoalcohol. The degree of monoesterification of
the carboxylic anhydride copolymer may range, for example, from
25-100% of the initial anhydrides, preferably from 50-80% of the
initial anhydrides. Additionally, the carboxylic anhydride vinyl
aromatic copolymer can be any partial monoester of the copolymer
which is soluble to any degree in basic pH solutions having a pH
greater than 8. Anhydride groups, ester groups, as well as free
acid groups or carboxylate salt groups may be present in the
carboxylic anhydride vinyl aromatic copolymer. As a particular
example, the anhydride-containing or acid-containing copolymer is a
styrene-maleic anhydride copolymer, particularly with a molar ratio
S:MA of styrene (S) to maleic anhydride (MA) ranging from about 1:1
to 3:1.
[0024] In a preferred example of this embodiment, the additive
composition comprises a combination of polymers. Exemplary additive
compositions of the present invention include, for example, an
ester functionalized polymer comprising a polymeric backbone and,
pendent thereon, one or more dicarboxylic acid moieties in at least
partial ester form; and a low molecular weight maleic anhydride
vinyl aromatic copolymer or an at least partial ester thereof. For
example, in at least one embodiment of the present invention, the
additive may include (i) an at least partial ester of a maleic
anhydride grafted hydrocarbon polymer and (ii) a low molecular
weight styrene-maleic anhydride (SMA) or an at least partial ester
thereof. In at least one embodiment of the present invention, the
low molecular weight styrene-maleic anhydride (SMA) is according to
Formula II:
##STR00003##
wherein n, R, x, y, and z are as described below.
[0025] The number of repeat units n may be from 7 to 72 and relates
to the molecular weight of this additive component. R can be any
residue of an aromatic, aliphatic, linear, or branched C1-C12
monoalcohol, preferably a C2-C8 monoalcohol. The monoalcohol may be
alkoxylated, such as with up to 16 alkoxy units from an ethoxy
group and/or a propoxy group. The SMA ester resin may have
different molar ratios of styrene (S)/maleic anhydride (MA)
co-monomer compositions, such as a molar ratio (x:(y+z)) in the
range from about 1:1 to 3:1 and more preferably from about 1.4 :1
to 1.6:1. The molecular variables x, y, and z, relate to the molar
ratios of S:MA such that x is from 1 to 4, a molar ratio of
(x:(y+z)) is in the range from about 1:1 to 3:1, and the
monoesterification molar ratio of (z/(y+z)) ranges from about 50 to
100%. The SMA ester resin can be any partial monoester of a
styrene-maleic anhydride resin that is soluble to any degree in
basic pH solutions having a pH greater than 8. These monoesters
have both acid and anhydride functionality. Particular examples of
monoalcohols which may comprise R of Formula II include, but are
not limited to, isopropyl and cyclohexyl alcohols. For example, the
additive composition may be an ether alcohol ester of a
styrene-maleic anhydride (SMA) copolymer, which defines a 75% total
monoester, and an S:MA ratio of between about 1.4:1 to about
1.6:1.
[0026] In one or more embodiments of the present invention, the one
or more dicarboxylic acid moieties pendant to the polymeric
backbone of the ester functionalized polymer are in accordance with
Formula II, wherein R.sup.1 and R.sup.2 can be the same or
different and are selected from H and any residue of an aromatic,
aliphatic, linear, or branched C1-C12 monoalcohol, preferably a
C2-C8 monoalcohol, subject to the proviso that in at least one of
the dicarboxylic acid moieties at least one of R.sup.1 or R.sup.2
is C1 to C12 alkyl. The monoalcohol may be alkoxylated, such as
with up to 16 alkoxy units from, for example, an ethoxy group
and/or a propoxy group. The one or more dicarboxylic acid moieties
may be, for example, from about 25 to 100% esterified. The one or
more dicarboxylic acid moieties may be at least partially
esterified with C1 to C6 aliphatic alcohols. In some embodiments,
the one or more dicarboxylic acid moieties contain one or two ester
groups having a structure --C(.dbd.O)OR wherein R is a C1 to C6
alkyl group.
[0027] The term "low molecular weight" according to the invention
generally means a weight average molecular weight less than 50,000.
When a low molecular weight carboxylic anhydride vinyl aromatic
copolymer, such as a styrene-maleic anhydride, is used as part of
an additive composition, the molecular weight may be affected by
the degree of monoesterification, among other factors. The
molecular weight of the styrene-maleic anhydride copolymer or resin
may thus range from 1,000 to 50,000, or more preferably from 2,000
to 15,000. Similarly, when the ester functionalized polymer
comprising a polymeric backbone and, pendent thereon, one or more
dicarboxylic acid moieties in at least partial ester form, such as
an at least partial ester of a maleated polybutadiene, is employed
as the additive, the molecular weight may vary depending on the
maleic anhydride content (e.g., the degree of maleinization) or by
the degree of monoesterification, among other factors. The weight
average molecular weight of the ester functionalized polymer may
thus be in the range from 250 to 25,000, or more preferably from
500 to 10,000. The weight average molecular weight ranges are as
measured by gel permeation chromatography (GPC) with polystyrene
standards in tetrahydrofuran (THF).
[0028] In another embodiment, the present invention is a caustic
removable hot melt adhesive composition, more particularly a hot
melt pressure sensitive adhesive composition, which includes a hot
melt adhesive additive. The hot melt adhesive composition is
caustic removable and includes a hot melt adhesive additive which
comprises an ester functionalized polymer comprising a polymeric
backbone and, pendent thereon, one or more dicarboxylic acid
moieties in at least partial ester form; and an adhesive resin
selected from the group consisting of styrene-isoprene block
copolymers, polyacrylate resins, poly ethylene vinyl acetate (EVA)
resins, polystyrene butadiene resins, random styrenebutadiene (SBR)
copolymers, styrene-butadiene block copolymers,
styrene-isoprene-butadiene-styrene (SIBS),
styrene-ethylene-propylene-styrene (SEPS),
styrene-ethylene-butylene-styrene (SEBS) block copolymers,
amorphous poly-.alpha. olefin (APAO) resins, and mixtures thereof.
In at least one particular embodiment, the additive composition
further comprises a low molecular weight .alpha.,.beta.
ethylenically unsaturated anhydride-containing or acid-containing
polymer selected from the group consisting of low molecular weight
maleic anhydride homo-polymers and at least partial esters thereof,
a low molecular weight maleic anhydride olefin copolymers and at
least partial esters thereof, and low molecular weight maleic
anhydride vinyl aromatic copolymers and at least partial esters
thereof, and combinations and mixtures thereof.
[0029] In a preferred example of this embodiment, the additive
composition comprises an ester functionalized polymer comprising a
polymeric backbone and, pendent thereon, one or more dicarboxylic
acid moieties in at least partial ester form; and a low molecular
weight maleic anhydride vinyl aromatic copolymer or an at least
partial ester thereof. For example, in at least one embodiment of
the present invention, the additive may include (i) an at least
partial ester of a maleic anhydride grafted hydrocarbon polymer and
(ii) a low molecular weight styrene-maleic anhydride (SMA) or an at
least partial ester thereof. The present invention has a particular
usefulness for labels on products which are to be recycled.
[0030] During manufacture of a caustic removable hot melt adhesive
composition according to one of the embodiments of the present
invention, an additive package is added during the compounding of
the adhesive. The additive package contains a combination of a low
molecular weight styrene-maleic anhydride copolymer ester and a
maleated grafted hydrocarbon polymer ester. The components of the
additive can be added in varying amounts. In some embodiments, from
0 to about 15 weight percent of each component of the additive is
used, such that at least one ester functionalized polymer
comprising a polymeric backbone and, pendent thereon, one or more
dicarboxylic acid moieties in at least partial ester form is
present in the additive. For an embodiment employing a low
molecular weight styrene-maleic anhydride copolymer ester and a low
molecular weight maleated grafted hydrocarbon polymer ester as
components of the additive, preferably from about 1 to about 12
weight percent of each component is used. More preferably, the
total weight content of the additive composition (i.e., total
weight content of all component polymers of the additive
composition) in the said hot melt adhesive composition is generally
at least 3%.
[0031] An exemplary conventional hot melt adhesive, to which the
additive of the present invention may be added, includes a
styrene-isoprene-styrene (SIS) block copolymer, a hydrocarbon (C5
or C9) tackifying resin, a rosin ester tackifier, and/or a process
oil. A SIS block copolymer may be employed in the hot melt
adhesive, such as that which is sold by Kraton Performance Polymers
Inc. of Houston, Tex. under the trade name Kraton D-1113. A C5
hydrocarbon tackifying resin may be utilized, such as that which is
sold by Cray Valley U.S.A. of Exton, Pa. under the trade name
Wingtack ET. A naphthenic process oil may be used in the hot melt
adhesive as well, such as the one sold under the trade name Nyflex
222B by Nynas AB of Stockholm, Sweden. As is known to one skilled
in the art, conventional hot melt adhesives may include a variety
of other components including, but not limited to, starches, waxes,
plasticizers, anti-oxidants, stabilizers, pigments, dyes, biocides,
flame retardants, antistatic agents, or fillers. For example, the
hot melt adhesive may include Ethanox 310, an antioxidant sold by
Albemarle Corporation of Baton Rouge, La.
[0032] The additive of the present invention may be introduced to a
conventional hot melt adhesive by any process known to one skilled
in the art. For example, when an SMA copolymer ester and maleated
polybutadiene ester are employed as the additive polymers, they may
be introduced separately from each other and separate from, or in
combination with, any of the individual components of the
conventional hot melt adhesive. As a further example, the additive
may be introduced to the components of a conventional hot melt
adhesive comprising a styrene-isoprene-styrene (SIS) block
copolymer, a hydrocarbon (C5-C9) tackifying resin, and a process
oil. The SMA ester may be prepared from a commercially available
low molecular weight styrene maleic anhydride copolymer product
with high maleic anhydride contents, such as that sold by Cray
Valley U.S.A. of Exton, Pa. under the trade name SMA. The maleated
polymeric hydrocarbon ester may also be a commercially available
product, such as that sold by Cray Valley U.S.A. of Exton, Pa. A
process oil, such as mineral oil, may be added last. The hot melt
adhesive containing the additive is allowed to mix on sigma blade
mixer until it is homogeneous.
[0033] In yet another embodiment, the present invention is a
caustic removable adhesive label comprising a substrate and a
caustic removable hot melt adhesive composition comprising a hot
melt adhesive additive. The hot melt adhesive composition can be
used in hot melt adhesive labels, preferably in hot melt pressure
sensitive adhesive labels, particularly for recyclable glass
articles which may be containers such as bottles. The labels can be
removed with caustic, for example in a hot caustic bath, when the
objects are recycled. The hot melt adhesive additive comprises an
ester functionalized polymer comprising a polymeric backbone and,
pendent thereon, one or more dicarboxylic acid moieties in at least
partial ester form; and an adhesive resin selected from the group
consisting of styrene-isoprene block copolymers, hydrocarbon
tackifying resins, polyacrylate resins, poly ethylene vinyl acetate
(EVA) resins, polystyrene butadiene resins, random styrenebutadiene
(SBR) copolymers, styrene-butadiene block copolymers,
styrene-isoprene-butadiene-styrene (SIBS),
styrene-ethylene-propylene-styrene (SEPS),
styrene-ethylene-butylene-styrene (SEBS) block copolymers,
amorphous poly-.alpha. olefin (APAO) resins, and mixtures thereof.
The adhesive composition is applied to the substrate for adhesion
to an article. Alternatively or additionally, the adhesive may be
applied to the article with the substrate or label applied thereon,
as would be appreciated by one having ordinary skill in the art.
The label of the present invention may be a label which, after
application of the caustic removable hot melt adhesive composition,
may be adhered to an article such as a glass bottle. In at least
one embodiment, the caustic removable adhesive label contains a hot
melt adhesive composition including an additive composition, in
which the additive composition comprises a combination of polymers.
Without being held to the theory, it is believed that the acid
and/or anhydride groups of the additive impart caustic solubility
to the adhesive composition despite the presence of insoluble
components such as styrene-isoprene-styrene (SIS) tri-block
copolymer, hydrocarbon tackifying resin, and/or process oil. The
present invention enables the manufacturing of a hot melt adhesive
which has favorable water resistance and viscoelastic properties
for adhesion to a substrate, for example the retention of a label
on a glass bottle, while also imparting caustic removability to the
hot melt adhesive formula. This allows for strong retention and
adhesion characteristics when they are desired, but also
removability of the hot melt adhesive from the substrate when it is
necessary as in the recycling process.
[0034] The hot melt adhesive containing the additive may be applied
to the label and/or the substrate by various processes known to one
skilled in the art. In one representative process, the caustic
removable hot melt adhesive of the present invention is melted and
poured onto a blade coater. The blade coater can be employed to
apply a thin film of the caustic removable hot melt adhesive to a
release liner to which a face stock is laminated. The laminate may
then be cut into label size strips for application to a substrate,
such as a glass bottle.
[0035] In a further embodiment, the present invention is an article
having a label adhered with a caustic removable hot melt adhesive
composition containing an additive as defined above. For hot melt
adhesive labels, particularly for hot melt pressure sensitive
adhesive labels, the adhesive is coated onto a release liner, which
is then immediately laminated with a label facestock, which could
be paper or plastic. The article may be, for example, a container
which may be made of any suitable material including, for example,
glass, metal (e.g., stainless steel), or plastic (e.g., high
density polyethylene). The label adheres to the article with good
adhesion properties, and the article and label are water resistant
(i.e., resistant to water having a substantially neutral pH). The
label becomes removable from the article upon being submerged in,
or otherwise treated with, a caustic bath having a pH greater than
8. The label is then applied to an article such as a glass bottle
for identification and/or decorative purposes. After the contents
of the article have been used, it may be desirable to recycle the
article. To remove the label, articles can be placed in a hot
caustic bath, which causes the adhesive to dissolve and/or
delaminate from the article. The clean bottle or other article can
then more easily be recycled without the contamination of the label
and/or the adhesive. Until now, it has not been possible to remove
conventional hot melt adhesive labels from articles in this way.
Removal of the hot melt adhesive is made possible by adding the
additive of the present invention.
[0036] Any process or component known in the art may be utilized to
esterify the additive components of the present invention. The
additive components may be esterified, for example, with an
alcohol, more particularly by a monoalcohol. For example, the
carboxylic anhydride vinyl aromatic monomer copolymer may be at
least partially esterified by an aromatic, aliphatic, linear, or
branched C1-C12 monoalcohol, preferably a C2-C8 monoalcohol. Also,
a mixture of such alcohols may be suitable. Some examples of
suitable alcohols are isopropyl, butyl alcohols, ether alcohols,
and 2-ethyl-1-hexanol. From a performance standpoint, a butyl
alcohol or ether alcohol is currently preferred. The alcohol is
provided so as to esterify between about 50 and about 85 mole
percent of the pendent dicarboxylic acid moieties of the polymer.
Typically, the esterification reaction does not go fully to
completion; thus, a slight excess of the alcohol is unreacted,
i.e., between about a 1 and about 5 mole % excess over the desired
degree of esterification. As known in the art, the rate of
esterification may be controlled or accelerated using a suitable
catalyst (e.g., acid, tin compounds). The advantageous properties
of this invention can be observed by reference to the following
examples, which illustrate but do not limit the invention.
EXAMPLES
Control Adhesive
[0037] The Control Adhesive (Formula 1) was compounded with typical
procedures known to those skilled in the art. SIS Polymer (Kraton
D1113) was first added with an anti-oxidant (Ethanox 310) to a hot,
approximately 150.degree. C., sigma-blade mixer under nitrogen
blanket. The SIS was masticated over approximately ten minutes.
After complete mastication of the SIS, hydrocarbon tackifying resis
(Wingtack ET) was added in three increments over approximately 30
minutes. After complete incorporation of the resin, process oil
(Nyflex 222B) was added over approximately 10 minutes.
Adhesive Composition Samples
[0038] Five adhesive formulas were prepared (Formulas 2 through 6)
each containing an additive comprising a partial ester of a low
molecular weight maleated polymeric hydrocarbon ester having a
number average molecular weight (Mn) of 370, a weight average
molecular weight (Mw) of 500, was 9% wt/wt maleated, and esterified
with butyl alcohol to an esterification ratio of 50%, in accordance
with at least one embodiment of the present invention. In some
formulations, the additive further contained a low molecular weight
product with high maleic anhydride content, a styrene:maleic
anhydride (S:MA) ratio of 1.5:1, a number average molecular weight
(Mn) of 2,900 and a weight average molecular weight (Mw) of 7,000,
and was esterified with an ether alcohol to an esterification ratio
of 75%. The molecular weight ranges were measured by GPC (gel
permeation chromatography) with polystyrene standards in THF
(tetrahydrofuran).
[0039] The caustic removable hot melt adhesive with additive was
prepared in the following general manner using the same general
procedure as the control adhesive. Adhesive Formulas 2 through 6
were compounded by first adding the SIS Polymer (Kraton D1113), the
SMA ester and the anti-oxidant (Ethanox 310) to a hot,
approximately 150.degree. C., sigma-blade mixer under nitrogen
blanket. The mixture was mixed until masticated over approximately
ten minutes. After complete mastication of the SIS, the hydrocarbon
tackifying resin (Wingtack ET) was added in three increments over
approximately 30 minutes. After complete incorporation of the resin
the liquid maleated polymeric hydrocarbon ester and the process oil
(Nyflex 222B) was added over approximately 10 minutes. Table 1
details the composition of the adhesive formulations tested.
TABLE-US-00001 TABLE 1 Sample Formulas Tested (in w/w %) Additive
Styrene- Hydrocarbon maleic SIS Block tackifying Process Anti-
Total Anhydride Copolymer resin Oil oxidant Weight Ester Maleated
C5 Sample (Kraton D- (Wingtack (Nyflex (Ethanox % of (SMA
Hydrocarbon Formula 1113) ET) 222B) 310) Additive Ester) Ester 1
41.3 49.5 8.2 1.0 0.0 0.0 0.0 (Control) 2 39.3 47.2 7.9 0.9 4.7 0.0
4.7 3 37.5 45.0 7.5 0.9 9.0 0.0 9.0 4 34.4 41.3 6.9 0.8 16.5 8.3
8.3 5 37.5 45.0 7.5 0.9 9.0 6.8 2.3 6 37.5 45.0 7.5 0.9 9.0 4.5
4.3
[0040] The sample formulas were initially tested for compatibility.
It is noted that the combination additive of the present invention
was found to be compatible with the components of conventional hot
melt adhesives. The caustic removable hot melt adhesive and
additive mixed uniformly during compounding with a Sigma mixer.
There was no phase separation at room temperature or in the
170.degree. C. oven-heated samples (i.e., uniform
cross-section).
[0041] Dynamic Mechanical Analysis was also performed on these
samples, using a TA Instruments Rheometer AR 2000 on an 8 mm
parallel plate. Dynamic Mechanical Analysis (DMA) is a
thermo-mechanical analytical technique used to study the
characteristics of materials such as the viscoelastic nature of
polymers and polymer blends. An oscillating force is applied to a
sample of material and the resulting displacement of the sample is
measured. The samples can be either solids, which are tested by
linearly applied strains, or melts or liquids, which are normally
tested in shear. The DMA sample deforms under the applied load.
From this the stiffness of the sample can be determined, and the
sample modulus can be calculated. It is possible to determine the
damping properties of a material by measuring the time lag in the
displacement compared to the applied force. The time lag is
reported as a phase lag angle. The damping is called tan delta
(.delta.), as it sis reported as the tangent of the phase lag.
Viscoelastic materials such as polymers typically exhibit the
properties of a glass (high modulus) at low temperatures, and those
of a rubber (low modulus) at higher temperatures. This change of
state, i.e., glass transition or alpha relaxation, can be observed
by scanning the temperature during a DMA experiment. The samples
were observed for broadening of the tan .delta. peak, and/or the
appearance of a second peak indicating a change of state, under the
DMA. Table 2, below, presents the numerical results of the Dynamic
Mechanical Analysis.
TABLE-US-00002 TABLE 2 Dynamic Mechanical Analysis Temp Temp
Storage Storage Peak 1.sup.st Temp 2.sup.nd 3.sup.rd Modulus
Modulus Sample Tan .delta. X-over X-over X-over G' (Pa) G' (Pa)
Formula (.degree. C.) (.degree. C.) (.degree. C.) (.degree. C.) at
25.degree. C. at 40.degree. C. 1 -7.6 -26.7 8.4 101.9 47240 33550
(Control) 2 -0.7 -17.9 15.5 107.9 41720 26410 3 -0.7 -16.7 14.4
107.9 42790 28470 4 -0.6 -16.8 15.4 105.9 50490 32610 5 -0.2 -15.8
15.4 108.9 46160 29060 6 -0.6 -16.9 15.5 106.9 44050 26010
[0042] The overall results, as shown in Table 2, demonstrate that
the essential viscoelastic performances of the adhesive composition
are not significantly affected when an additive according to an
embodiment of the present invention is added to a conventional hot
melt adhesive. Visual observations were made of the formulations in
a Sigma mixer, of oven heated samples heated to 170.degree. C., and
of the applied film during coating. The results showed compatible
transparent adhesive films for the adhesive of the invention
containing the additive.
[0043] An adhesive label of the present invention may be prepared
by various methods known to one having ordinary skill in the art.
In one preferred embodiment, the adhesive is melted and poured onto
a blade coater so that a thin film of it can be applied to a
release liner to which a face stock is laminated. The laminate is
then cut into label size strips. To test the label, the release
liner is removed and the label is applied to a substrate and rolled
with a 4.5 lb. roller. Typical adhesive properties such as tack,
peel and shear can be measured and compared with adhesives not
containing the combination additive of the present invention. For
adhesion tests, the adhesives were heated to 170.degree. C. and
coated onto a release liner and immediately laminated to a 2 mil
thick (50 micron) polyethylene terephthalate (PET) polyester film.
The initial adhesive properties were measured after aging the
coated adhesive sheets for 24 hours at 23.degree. C. and 50%
relative humidity (R.H.). Aged adhesive properties were measured
after aging the coated sheets for 1 week at 70.degree. C. followed
by a minimum of 24 hours at 23.degree. C. and 50% R.H. The aged
adhesion results, when compared to the initial adhesion properties,
showed that the adhesion properties were not significantly
different.
[0044] The sample formulas were tested using standard test methods
established by the Pressure Sensitive Tape Council (PSTC). The
sample formulas were tested for peel strength, according to PSTC
Method 101 "International Standard for Peel Adhesion of Pressure
Sensitive Tapes." Peel adhesion is the force required to remove a
pressure sensitive tape from a test panel or its own backing at a
controlled angle and at a standard rate and condition. The sample
formulas were tested for their adhesion to high density
polyethylene (HDPE), stainless steel (SS), and glass substrates at
an angle 180 degrees. The sample formulas were further tested using
HDPE, SS, and glass substrates for loop tack under PSTC Method 16.
The results of these tests are shown in Table 3 below.
TABLE-US-00003 TABLE 3 Initial Adhesion Performance SMA Ester/
Maleated Peel Adhesion Loop Tack Adhesion C5 on on on on Hydro- on
SS Glass HDPE on SS Glass HDPE Sample carbon Total N/m N/m N/m N/m
N/m N/m Formula Ester Additive % (lbf/in) (lbf/in) (lbf/in)
(lbf/in) (lbf/in) (lbf/in) 1 0.0/0.0 0.0 1219 (7.0) 1042 (6.0) 358
(2.0) 1102 (6.3) 849 (4.9) 431 (2.5) (Control) 2 0.0/4.7 4.7 1146
(6.5) 1079 (6.2) 444 (2.5) 1122 (6.4) 1220 (7.0) 385 (2.2) 3
0.0/9.0 9.0 1275 (7.3) 1072 (6.1) 549 (3.1) 1190 (6.8) 1196 (6.8)
519 (3.0) 4 8.3/8.3 16.5 715 (4.1) 675 (3.9) 436 (2.5) 787 (4.5)
910 (5.2) 371 (2.1) 5 6.8/2.3 9.0 1172 (6.7) 931 (5.3) 468 (2.7)
932 (5.3) 995 (5.7) 417 (2.4) 6 4.5/4.5 9.0 1241 (7.1) 1088 (6.2)
637 (3.6) 1045 (6.0) 1048 (6.0) 486 (2.8)
[0045] Additionally, the shear adhesion failure temperature was
measured for each of the samples. The recorded shear adhesion
failure temperature for each of the samples was 65.4.degree. C. for
the control sample 1, 62.9.degree. C. for sample 2, 64.5.degree. C.
for sample 3, 67.1.degree. C. for sample 4, 67.8.degree. C. for
sample 5, and 65.4.degree. C. for sample 6.
[0046] The components of the adhesive may be adjusted to achieve
specifically desired adhesion properties. The amount of each
component can be varied to balance adhesion characteristics and
initial compatibility with conventional hot melt formulations,
while increasing water-resistance and caustic removability. For
example, when a combination of SMA ester and maleated C5
hydrocarbon ester is used as the additive, a limited and acceptable
decrease in overall adhesive properties was identified by the peel
and loop tack tests. However, the combination additive was very
compatible with conventional hot melt adhesive formulas containing
SIS block copolymers, hydrocarbon resins, tackifier resins, and
process oil with overall unaffected viscoelastic performance
metrics, as shown in Table 2 above.
[0047] The additive of the present invention was found to be
compatible with conventional hot melt adhesives while also enabling
them to be caustic removable. This additional characteristic is
useful for many purposes, particularly in the recycling process.
Samples of Formulas 1 through 6 were tested for caustic
removability. The adhesive Formulas were heated to 170.degree. C.
and coated onto 12 inch by 1 inch (30.48 cm by 2.54 cm) adhesive
strips of unbleached Kraft 30 lbs/ream paper to test caustic
removability and cold water resistance. The labels were adhered to
flat glass panels and rolled with a 4.5 lb roller. The glass panels
were immersed in a hot caustic bath consisting of 2.5% sodium
hydroxide in water, heated to 80.degree. C. Slight agitation was
applied to the caustic bath.
[0048] The samples were timed for how long it took to remove the
labels from the panels and the adhesion was rated for the amount of
adhesive residue left on the panels. Glass panels are kept immersed
in the aqueous solution of NaOH at 2.5% at 80.degree. C. for a
maximum of 5 minutes. Then, the strip adhesion (i.e., caustic
removability) is measured and given a rating from 0 to 5, where 5
represents easy removal from the panel and no residue left on the
panel and 0 represents no removal of the test strip (i.e., the
adhesive remains on the panel).
TABLE-US-00004 TABLE 4 Caustic Removability Tests Total Sample
SMA/Maleated Polymeric Additive Rate of Formula Hydrocarbon Ester
(wt %) Removability 1 (Control) 0.0/0.0 0.0 0 2 0.0/4.7 4.7 1 3
0.0/9.0 9.0 1 4 8.3/8.3 16.5 5 5 6.8/2.3 9.0 5 6 4.5/4.5 9.0 5
[0049] The results in Table 4 above show that the samples
containing an additive composition containing both SMA ester and
maleated polymeric hydrocarbon ester (i.e., samples 4, 5, and 6)
are easily removable with a rate of 5 on glass. As would be
appreciated by one having ordinary skill in the art, and as
discussed above, the additive composition and the adhesive
composition may be formulated to achieve specifically desired
adhesion properties. The amount of the additive components can be
varied to balance adhesion characteristics and initial
compatibility with conventional hot melt formulations, while
increasing water-resistance and caustic removability.
[0050] While preferred embodiments of the invention have been shown
and described herein, it will be understood that such embodiments
are provided by way of example only. Numerous variations, changes,
and substitutions will occur to those skilled in the art without
departing from the spirit of the invention. Accordingly, it is
intended that the appended claims cover all such variations as fall
within the spirit and scope of the invention.
[0051] The present invention, therefore, is well adapted to carry
out the objects and attain the ends and advantages mentioned, as
well as others inherent therein. While the invention has been
depicted and described and is defined by reference to particular
preferred embodiments of the invention, such references do not
imply a limitation on the invention, and no such limitation is to
be inferred. The invention is capable of considerable modification,
alteration and equivalents in form and function, as will occur to
those ordinarily skilled in the pertinent arts. The depicted and
described preferred embodiments of the invention are exemplary only
and are not exhaustive of the scope of the invention. Consequently,
the invention is intended to be limited only by the spirit and
scope of the appended claims, giving full cognizance to equivalents
in all respects.
* * * * *